Metallurgical apparatus



metallurgical furnaces will be obvious.

Patented July 20, 1948 UNITED STATES PATENT OFFICE rm'rmnnarcannrrnaa'rus Harry E. McDonnell, Steubenville, Ohio Application m 5, 1947, Serial No. 782,598

2 Claims. -1

The present invention relates to the maintenance of uniform conditions in metallurgical furnaces. More specifically, the present invention relates to an improved apparatus for supplying a stream of oxygen-containing gas at substantially uniform temperature to a plurality of points in a metallurgical furnace.

Th invention is especially suited to blast furnace operations although its application to other In blast furnace operation an oxygen-containing gas, at present air, is fed at an elevated temperature to the base of the furnace to effect combustion of the coke and reduction of the we. The heated air is introduced adjacent the hearth of the furnace through a plurality of tuyeres symmetrically arranged around the circumference of the lower portion of the furnace. The heated air is supplied to the tuyres from a circular pipe in the form of a manifold, commonly called the bustle pipe, which in turn receives the heated air at one point from a hot blast main. Th air supplied is first compressed and then heated in one of a plurality of stoves. The stoves include a mass of refactory brickwork and operate on the regenerative system, the number of stoves being such that one is supplying heat to the blast while the others are being heated. When the compressed cold air is first admitted to one of the stoves to be heated, the temperature of the blast issuing from the stove is a maximum and as the stove cools off the temperatur of the blast reaches a minimum at which time the cold air blast is directed to one of the other stoves. Again the hot blast issuing from this stove is at a maximum temperature and the cycle is repeated. In order to minimize fluctuations in temperature of the ,hot blast supplied to the furnace, provision is made to supply through a by-pass a portion of the compressed cold air varying in amount so as to maintain the temperature of the hot blast supplied to the furnace at the desired operating temperatu-re. For this purpose the compressed cold air is normally fed into the hot blast main at a point far removed from the furnace so.that mixing of the heated air from the stoves with this cold air will be accomplished in some degree.

Nevertheless, since space requirements dictate that the stoves must be arranged in a. series along the hot blast main,when those stoves nearest the furnace are supplying heated air the length of hot blast main is insuflicientto allow thorough mixing of the hot and cold streams of air. Additionally, due to the high velocities encountered in the streams of air, the connections-from the Ill .ditions in blast furnace operation deleteriously affects overall operation.

blast. This accomplishes the desired mixing. but

besides the increased expense required by the necessary conduit connections, the chilling effect of the cold air introduced into the combustion well of the stove has a destructive eflect on -the brickwork at that point.

I have invented an improved apparatus for accomplishing this purpose with a minimum expense and additional structure. The present invention utilizes the hot blast main between the furnace and the stove nearest the furnace as a mixing chamber and by creating turbulence at this point effectively mixes the hot and cold blasts to deliver a resultant stream of hot blast of uniform temperature at the tuyres; No maintenance problems are introduced, The greatest advantages of my invention ar based on its simplicity coupled with its effectiveness in solving a difllcult problem.

This application is a division of application Serial Number 513,271, filed December '1, 1943,

now Patent2,418,654. M

An important object of the present inventionis to provide an improved apparatus for obtaining uniform conditions of blast in a metallurgical furnace,

A further important object of the present invention is the provision of an improved apparatus for mixing streams of heated oxygen-containing gas and cold oxygen-containing gas prior to introduction to a metallurgical furnace.

Referring to the drawings which disclose apparatus according to the present invention,

Figure 1 is a plan view, partially diagrammatic, of a form of the apparatus with the furnace shown in section and parts broken away to illustrate the invention more clearly.

Figure 2 is a view in longitudinal section of part of a hot blast main showing an embodiment of cated at III, a section being taken through this wall above the tuyeres. A bustle pipe is indicated at I I connected to the tuyeres (not shown) by pen stocks I2, I3, II and I5. Additional pen stocks are shown for connection with the remaining tuyeres. This figure being in plan view, the hearth of the furnace shows at I8. Connected at one side of the bustle I I is a hot blast main II and connected to the hot blast main by conduit I8, which normally includes a hot blast valve (not shown), is a stove I9 of'any desirable type. A plurality of additional stoves are connected in like manner to hot blast main II. At a point on hot blast main I1 beyond the farthest stove there is a connection to a bypass conduit from the cold blast main. Since this latter structure is conventional, it has not been shown. Between the connection of stove I9 and hot blast main I'I, there is a restriction in the hot blast main indicated at 20. pose of restriction is to change the pressure and velocity of the air at this point and thereby achieve mixing of the streams of air in the hot blast main, these streams being made up of the stream of hot air from the stove and the stream oftcold air from the bypass conduit.

Referring to Figures 2 and 3, a modification of the restriction 20 will be seen. In this embodiment the hot blast main which comprises a steel casing or shell 2i lined with firebrick and insulating brick 22 in the usual manner has the lining built up to one form of configuration suitable for achieving my purpose. Brickwork 22 is shaped to form a Venturi throat 23 merging into the walls of the hot blast main by means of truncated cone surfaces 24, 25 following the conventional Venturi tube construction. In the case of this embodiment, a mixing ofthe streams of air in the hot blast main is achieved by means of the well-known characteristics of the Venturi tube.

The modification shown in Figures 4 and 5 discloses a difierent apparatus for accomplishing the same purpose as that in Figures 2 and 3. Here a conduit 28 from a stovesupplies hot gas to the hot blast main indicated at 2'! in an ar- The purn rangement similar to that shown in Figure 1.

In this case, however, conduit 28 has off-center connection with the hot blast main 21 so that the hot stream from the stove enters the cold stream from the by-pass conduit in such a manner that rotation of the resultant stream takes place.

In an installation of the invention in a blast furnace with an arrangement similar to that in Figure 1 and using a restriction like that shown in Figures 2 and 3, highly satisfactory results were achieved. In this installation the velocity of the air in the hot blast-main varied from about feet per secondto feet per second, depending upon the temperature and volume of the blast. The temperature of the hot blast issuing from the stove was around 1800 F. while the temperature, of the cold blast being introduced into the hot blast main from the by-pass conduit was about 200 F. The quantity of cold blast was controlled to give an average temperature around 1200 F. at the bustle'plpe, although for operating reasons the temperature at this point is varied from about 900 F. to about 1200 F. The temperature diil'erential at the tuyeres corresponding to pen stocks II and I5 shown in Figure 1 ranged from 15 to 20 F. with a maximum of 50 F. when a large amount of cold blast and the stove nearest the furnace were being used. In a similar installation not utilizing the present invention, the temperature differential at these points varied from 50 to 150 F. with a maximum around 200 F. where a large amount of cold blast and the stove nearest the furnace were being used.

Since eiiicient and economical operation of a blast furnace calls for uniform conditions throughout, it will be apparent that the present invention contributes greatly toward improved operation. The temperature differential present where the present invention is not used introduces lack of uniformity of critical conditions by influencing the weight of air introduced on either side of the furnace and by producing a difierence in the sensible temperature of the air at these points. By means of a simple modification of existing structure or the incorporation of the simplified structure disclosed herein in a new installation, an improved structure is achieved with a minimum of expense and no new maintenance problem.

I claim:

1. In a metallurgical furnace having a plurality of points of injection of an oxygen-bearing gas for combustion therein. a manifold conduit supplying the gas to such points, a connection on the manifold conduit for supplying the gas thereto symmetrically arranged with respect to the. points of injection, a source for supplying a stream of the gas cold and a source for supplying a stream of the gas hot, the combination comprising a first conduit connected to the first named source, a second conduit connected to the second named source, a third conduit connecting the first and second conduits to said connection on the manifold conduit, and the second conduit having oiI-center connection with the third conduit to induce rotation of a stream of gas passing therethrough to thereby mix the component streams of cold and hot gas.

2. In a blast furnace having a plurality of tuyeres, a horizontally disposed bustle pipe connected therewith, a stove for supplying a stream of hot gas, and a source for supplying a stream of cold gas, the combination comprising a hot blast main adjacent the stove connected at one end with the bustle pipe and connected at a point removed therefrom with the source of cold gas, a stove connection on the side of the hot blast main at a point between the cold gas connection and the bustle pipe connection. a conduit between the stove and the stove connection on the hot blast main for conducting the stream of ,hot gas from the stove'into the hot blast main,

the stove connection on the hot blast main being oil-center with respect to the axis of the hot blast main whereby rotation of the resultant gas stream is induced in the hot blast main.

HARRY E. McDONNELL. 

